2.2 Quiz

Lewis Structures:

  • if it’s a halogen, with 7 valence electrons, it can only form one bond

  • if it has 6 valence electrons, it can form a double bond

  • if it has 5 valence electrons it can form a triple bond

  • if it has 4 valence electrons it can form a triple bond as well

  • the atom has to be responsible for as many indivisual electrons as there are valence electrons

  • sulfur and phosphorus are exceptions because they can surpass the octet rule; this is because they have empty d orbitals that can be filled with extra electrons, giving rise to the possibility of an expanded octet

Formal charge:

  • Valence electrons-electrons in lone pairs-# of bonds

  • the goal is for the formal charge to be zero on most of the atoms

  • each charge adds to the overall charge

Resonance structures:

  • molecular compounds with more than 1 possible lewis structure

VSEPR Shapes

  • linear if there are 2 atoms bonded to the central atom and zero lone pairs

    • 180 degrees

  • linear if there are only 2 atoms; can’t make a shape

    • 180 degrees

  • bent if there are 2 atoms bonded to the central atom and one lone pair

    • a little <109.5 degrees

  • bent if there are 2 atoms bonded to the central atom and 2 lone pairs

    • a little <109.5 degrees

  • trigonal planar if there are 3 atoms bonded to the central atom and 0 lone pairs

    • 120 degrees

  • trigonal pyramidal if there are 3 atoms bonded to the central atom and 1 lone pair

    • a little <109.5 degrees

  • tetrahedral if there are 4 atoms bonded to the central atom and 0 lone pairs

    • 109.5 degrees

Electronegativity and Intermolecular Forces

  • types of bonds

    • london dispersion, in all molecules

    • dipole-dipole, in polar molecules

    • hydrogen bonding in polar molecules with H-F, H-O, H-N bonds

  • compound is nonpolar if

    • the central atom has 0 lone pairs

    • all atoms around central atom are the same

  • dipole moments point toward the most electronegative molecules

    • bond polarity is toward the more electronative atom

    • molecular polarity is the overall dipole moment

  • pauling scale

    • If the electronegativity is

      • <0.4, nonpolar

      • 0.4-1.7, polar

      • >1.7, ionic

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